I've had a problem where IP/TV 3.2 clients that are watching a stream with a Screencaster will no longer update the slide when the presenter flips to the next one. MPEG-1 audio and video continue to run without problems on the viewer. Doesn't matter whether clients are in the same VLAN or others. Clients are all 100/FDX. Sometimes a client will go 100 slide flips, sometimes only 10 before it loses sync. (I've got the powerpoint set to advance every 5-6 seconds)
Looking at the switch shows that the client is still in the multicast group.
Stopping a restarting the client usually gets it back in-sync with the slides.
Running PowerPoint 97, Screencaster is in "JPG" mode, no slide animations.